Interaction of Magnetic Crystals with Radiation in the Range 104–105 cm−1

The optical absorption spectrum of magnetic crystals containing ferric iron in the range 104 to 105 cm−1consists of a series of sharp peaks superimposed on a strong absorption band. The absorption band is associated with a large Faraday rotation of the transmitted light. The sharp peaks are identified as transitions within the configuration (3d5). The broad band can arise either from an internal transition to (3d44p)or to a charge transfer process. Both mechanisms are able to account for the observed intensity and rotation within a factor of two. Because of the Faraday rotation, the charge transfer must be associated with d levels of symmetry Γ5. The rotation has the opposite sign for the two cases and could be used to distinguish between them.